N-acetyl-D-glucosamine is a monosaccharide that makes up chitin contained in shells of crustacea such as crab and shrimp and is a nutrient contained in an extremely small amount in foods, and is also produced from chondrocytes in the body. N-acetyl-D-glucosamine is considered to have similar effects to that of glucosamine, and ingestion of N-acetyl-D-glucosamine is known to induce generation of novel cartilage and stop progression of osteoarthritis, or in some cases, to cure osteoarthritis (J. New Remedies and Clinics Vol. 52, No. 3, pp. 301-312, 2003). While glucosamine has a bitter taste, N-acetyl-D-glucosamine has a sweet taste 50% as sweet as sucrose and can be easily ingested, and therefore, N-acetyl-D-glucosamine has attracted attention as an alternative substance to glucosamine.
A conventional method of producing N-acetyl-D-glucosamine is performed by using shells of crustacea such as crab and shrimp as raw materials. Here is the outline of the method: N-acetyl-D-glucosamine is produced by steps of: crushing shells of crustacea; decalcifying the crushed products with a dilute acid; removing proteins with an alkali to yield purified chitin; hydrolyzing the resultant chitin with an acid to produce glucosamine; and then acetylating the resultant glucosamine with anhydrous acetic acid.
Meanwhile, conventional methods also include: a method involving partially hydrolyzing purified chitin with an acid (for example, see Patent Document 1); a method of producing N-acetyl-D-glucosamine by degrading chitin as a raw material with an enzyme produced by a microorganism_(for example, see Patent Document 2 and Patent Document 3); and a method involving partially hydrolyzing chitin with an acid and allowing an enzyme to react with the hydrolysate (for example, see Patent Document 4).
Conventional methods also include other production methods such as: a method of producing N-acetyl-D-glucosamine by culturing either chlorella cells infected with Chlorovirus or recombinant Escherichia coli introduced with a gene derived from Chlorovirus (for example, see Patent Document 5); and a method of producing N-acetyl-D-glucosamine by fermentation using a genetically modified microorganism, specifically, a genetically modified Escherichia coli (for example, see Patent Document 6).    Patent Document 1: JP 2000-281696 A    Patent Document 2: JP 2000-513925 A    Patent Document 3: JP 2004-41035 A    Patent Document 4: JP 63-273493 A    Patent Document 5: JP 2004-283144 A    Patent Document 6: WO 2004/003175